1. Field of the Invention
The invention relates to the rotational casting of olefin polymer-based compositions.
2. Description of the Prior Art
In order to obtain maximum physical properties, polyolefins, such as polyethylene, which are used in rotational molding compositions or processes must be highly stabilized. Typical stabilizers which might be used in this regard are 2,6-di-tert-butyl-para-cresol, and dilauryl thiodipropionate. When the polyolefin-based compositions, however, are stabilized with such stabilizer systems, problems arise with respect to pinholes on the surfaces of the molded part or object which is formed in the rotational molding or casting process. Whereas an unstabilized resin-based system provides a molded object having inferior physical properties but which is free of surface pinholes, the stabilized system provides a molded object which has vastly improved physical properties, but which has surface pinholes. The surface pinholes are particularly objectionable on the molded object when the molded object must subsequently be painted. The paint will not bridge across the pinholes with the result that a severely spotted pinhole surface results. Thus, prior to the present invention, polyolefin-based rotational molding compositions which were highly stabilized had to be used for molding unpainted articles or else the manufacturer thereof had to resign himself to accepting a severely spotted, painted, molded object.